1. Field of the Invention
The present invention relates to a display device, and more particularly, to a display device with integrated in-cell type touch screen and a driving method thereof.
2. Discussion of the Related Art
Touch screens are a type of input device that is included in display devices such as liquid crystal display (LCD) devices, field emission displays (FEDs), plasma display panels (PDPs), electroluminescent displays (ELDs), and electrophoretic displays (EPDs), and enables a user to input information by directly touching a screen with a finger, a pen or the like while looking at the screen of the display device.
Particularly, the demand for display devices with integrated in-cell type touch screen, which include a plurality of built-in elements configuring the touch screen for slimming portable terminals such as smart phones and tablet personal computers (PCs), is recently increasing.
In a related art display device with integrated in-cell type touch screen disclosed in U.S. Pat. No. 7,859,521, a plurality of common electrodes for display are segmented into a plurality of touch driving areas and touch sensing areas, thereby allowing a mutual capacitance to be generated between the touch driving area and the touch sensing area. Therefore, the related art display device measures a mutual capacitance change that occurs in touch, and thus determines whether there is a touch.
In the display device with integrated in-cell type touch screen, a driving pulse is applied to common electrodes corresponding to a touch driving area when a panel operates in a touch diving mode in order for each of the common electrodes to perform a function of a touch electrode.
A driving pulse applied to common electrodes corresponding to a touch driving area generally has a square type. An RC load is caused by a length between a common electrode formed in the touch driving area and a circuit unit applying the driving pulse, and for this reason, RC delay occurs in a waveform applied to the touch driving area, causing a distortion of the waveform. As a result, as the distance becomes farther away from the circuit unit, an RC delay deviation increases, and thus, a time taken in charging the touch driving area is changed. For this reason, a deviation of and a reduction in touch performance occur in each touch driving area.